#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<cstdio>
#include<algorithm>
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
const int maxn=2e5+1000;
typedef long long LL;
inline LL read(){LL x=0,f=1;char ch=getchar();	while (!isdigit(ch)){if (ch=='-') f=-1;ch=getchar();}while (isdigit(ch)){x=x*10+ch-48;ch=getchar();}
return x*f;}
char str[maxn];
char p[maxn];
LL tot=0;
int main(void)
{
  cin.tie(0);std::ios::sync_with_stdio(false);
  LL n,k;cin>>n>>k;
  cin>>(str+1);
  for(LL i=1;i<=k;i++){
     p[i]=str[i];
  }
  for(LL i=1;i<=k;i++){
    for(LL j=i+k;j<=n;j+=k) p[j]=p[i];
  }
  //LL j=1;
  bool flag=1;
  for(LL i=1;i<=n;i++){
     if(p[i]<str[i]){
        flag=0;
        break;
     }
  }
  //cout<<"flag="<<flag<<"\n";
 // cout<<"tot="<<tot<<"\n";
  if(flag==0){
    LL temp=n;
    while(p[temp]=='9') p[temp]='0',temp--;
    p[temp]++;
  }
  cout<<n<<"\n";
  for(LL i=1;i<=n;i++){
    //if(i%k==0) cout<<p[tot];
    ///else cout<<p[i%k];
    cout<<p[i];
  }
  cout<<"\n";
return 0;
}
